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Photo: A close up of a Microscope

Under the microscope: the immune system

Sarah Foxton

The immune system is a puzzle that scientists across the globe are trying to solve.

The role it plays in MS is a complicated one, but research is ongoing to better understand this. Let’s take a look at the latest.

Time to re-write the textbooks?

It might seem fair to assume that scientists know all there is to know about human anatomy and what everything does in the body. Or do they?

Consider the lymphatic system, a vital component of the immune system. It allows waste fluid to drain from tissues into the blood via a network of lymphatic vessels. Whilst in the lymphatic system, white blood cells can destroy bacteria and infections that have come from the tissues.

Up until now the interaction between the brain and the immune system has been seen as somewhat of a mystery. The entry and exit of immune cells from the brain is poorly understood.

Lymphatic breakthrough

However all that might be about to change. A recent study has uncovered what appear to be lymphatic vessels in the brain of a mouse. Researchers found that these previously unidentified structures contained the same type of immune cells found in the fluid that circulates in the lymphatic system. They were also able to confirm that the vessels were different in structure to those found in the cardiovascular system, which means they can’t be blood vessels.

The mysterious vessels were seen to be draining fluid. This suggests a brand new pathway for immune cells to leave the brain.This may shed new light on the causes of the inflammation and nerve cell death in the brain that are associated with conditions like MS.

More research is needed before we know if the results will be similar in humans or whether these vessels might play a role in MS.

When T-cells go bad

Other recent studies have delved a bit deeper into the immune system to look specifically at T cells, one type of immune cell that attacks the myelin sheath in MS. Normally, the brain is protected from the attack of T-cells by the blood brain barrier. When someone has MS, they sometimes have leakages in this barrier which means T-cells can move into the brain and attack. There are different types of T-cells, including the myelin reactive form, which are interesting when considering MS but are also present in people without MS.

One study set out to look at the difference in these particular T-cells between people with MS and those without. The study showed that the proteins produced by the myelin reactive T-cells were different in the two groups. This is significant because it is these proteins that determine how the cell functions. The subjects without MS had T-cells which produced protective proteins, whereas those with MS produced proteins which cause inflammation.

The not so helpful ‘Helper’ molecule

A separate study which also looked at these inflammatory T-cells has identified a molecule (called MCAM) which helps them to move across the blood brain barrier into the brain. Scientists showed that in an animal model of MS, if they blocked the activity of this helper molecule with a drug, then disease activity decreased.

The researchers are now proposing to put this drug into a clinical trial which highlights the significance of this finding. These studies are in the early stages but identifying some of these key molecules is essential for providing future drug targets.